BP Sunbury Undercroft, UK

Adding Life to Concrete – How MARKHAM carried out remedial works to and applied hydrogel waterproofing systems to an existing undercroft car park structure in Sunbury-on-Thames, England.

This concrete repair project, at the major BP site at Sunbury-on-Thames, UK, was carried out to address active leaks, corrosion, and deterioration in the undercroft structure.

OBJECTIVE

The existing car park roof / soffit slab was cracked and leaking quite extensively, causing damage to vehicles parked in the undercroft car park area. The leaks were also causing rebar corrosion and consequently, concrete degradation, creating unsightly calcification to the concrete and in the long-term, structural damage to the concrete structure. The objective therefore was to seal the existing cracks and waterproof the concrete soffit to, firstly protect the vehicles from damage and secondly, extend the operational lifespan of this asset.

This BP Sunbury concrete repair work was essential to prevent further deterioration and protect the integrity of the undercroft structure.

SOLUTION

MARKHAM was able to assist with a holistic three-part system. The cracks in the concrete soffit were sealed with resin injection work. This included both “live” or wet/leaking cracks and dry cracks that weren’t actually showing signs of leaking at that point. Concrete patch repairs were also carried out to remediate spalled areas. All electrical and drainage penetrations in the soffit were sealed with a combination of concrete repair mortars and/or resin sealants.

This BP Sunbury concrete repair process ensured the structure received consistent protection across all treated areas. Once these remediation works had been completed, the whole of the soffit area and columns were made waterproof by the high-pressure spray application of the AQURON 2000 treatment.

RESULTS

The resin injection work and concrete patch repairs halted and/or reversed the existing damage that the structure had already experienced. Traditionally, the risk associated with this type of remediation is that sealing up these leak points will push or transfer the leak points to other areas of the structure, setting up the possibility of transferring the concrete degradation elsewhere.

Waterproofing the matrix of the concrete soffit with the AQURON 2000 significantly reduces the possibility of these leaks occurring elsewhere in the structure. The application of AQURON 2000 also prevents the possibility of incipient anode corrosion between the repair materials and the original concrete structure. As the AQURON 2000 treatment penetrates up to 125mm into the concrete soffit and remains within the matrix of the concrete for the lifetime of the structure, this is a maintenance-free solution adding life to this concrete structure.

This BP Sunbury concrete repair project highlights the importance of addressing leakage and corrosion early. By completing structural crack injection and durability treatments, the undercroft gained long‑term protection and reduced future maintenance risk. This approach ensures a more reliable structure and supports better lifecycle performance.

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For reference on concrete repair practices, see the Concrete Society guidelines: https://www.concrete.org.uk